1. Field of the Invention
The present application is generally directed to building materials, and more specifically, to the packaging of prefinished fiber cement articles.
2. Description of the Related Art
In the construction industry, building materials are often prefinished with a coating prior to sale and installation. For example, prefinished siding planks and panels are popular because of the labor and time saved during installation; a siding contractor need only install the material on the exterior of a building, and no subsequent finishing, such as priming and painting, is required. Producing prefinished articles can be a boon for manufacturers as well. By finishing building materials before they leave the factory, a manufacturer has complete control over the quality and consistency of the finished article, which ensures that a coating with appropriate performance is applied and that the coating will have a predictable service lifetime.
Traditionally, unfinished siding planks and panels are stacked one atop another on a wood pallet, secured to the pallet with metal or plastic bands and wrapped with plastic or placed in bags to protect the siding from damage by the elements during transport, handling, and storage. Prefinished siding planks typically require additional packaging and protection to maintain the integrity and appearance of the factory-applied coating. In packaging prefinished siding composites such as hardboard or OSB siding, a protective layer of plastic film, foam, or paper between two siding planks or panels has been used to protect the prefinished surface. These protective layers are generally applied without an adhesive. Automated application is less accurate absent an adhesive to anchor the protective layer to the article. Consequently, such protective layers are typically applied manually, which is expensive and limits throughput. Also, loosely applied protective layer often becomes displaced during transportation of the article. Packaging prefinished planks and panels made from fiber cement presents a special problem because the abrasive nature of fiber cement may damage the protective layer and the prefinished article surface during storage, transport, and handling of the fiber cement articles.
In a typical manufacturing operation for fiber cement siding planks, several planks are cut from a single sheet. These planks are then finished and packaged separately such that the finished planks are individually placed back-to-back and front-to-front with a protective layer sandwiched either between planks, or sometimes between those planks stacked front-to-front to protect the prefinished surface. Stacking in this configuration prevents the abrasive backside of the plank or panel from contacting the prefinished front. Stacking planks back-to-back and front-to-front requires a means to flip the planks in the stacking operation, either manually or mechanically, thereby requiring additional labor or a piece of equipment built for this purpose, which adds additional equipment capital, operating, and maintenance costs.
In addition to protecting the prefinished faces of the fiber cement articles, the protective layers, also known as slip sheets, help keep the finished surfaces clean. The protective layers also protect the finished surfaces from damage by dirt and moisture. The protective layer can also be used for inhibiting efflorescence.
Sheet adhesion is affected by the variations of moisture content in finished fiber cement articles and the board surface temperature of finished surface. When using an adhesive to hold the slip sheets in place on the planks, adhesion becomes an important consideration. Too little adhesion results in the slip sheet falling off prematurely while too much adhesion can damage the plank or leave undesirable residue when the slip sheet is removed. With aging or storage, the adhesion changes with variations of moisture content in finished fiber cement articles, variations of the board surface temperature of finished surface, temperature history during storage, moisture history in storage, the UV exposure, the varied stacking pressure, and combined effects from the aforementioned variables. In some cases, the protective layers themselves damage the finished surfaces, for example, changing the glossiness of the finish (e.g., burnishing), changing the color of the finish, residue from protective layer remaining after removal, or removing portions of the finish when the protective layer is removed from the finished surface. A protective layer may also trap undesired moisture against the finished surface.